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Why cement emissions matter for climate change (2018)

151 points by Reedx 7y ago

colechristensen 7y ago
This analysis seems to skip the obvious step whereby the manufacture of cement involves expelling CO2 from limestone so that it can be mixed with water which re-forms the same compound by absorbing CO2. Making Lime CaCO3 (+ heat) → CaO + CO2 Making concrete CaO + CO2 (in water, from air) → CaCO3 [there are lots of other things in concrete, but the CaO/CaCO3 are the media that glue them together into the useful composite they are] They quote that as "half" the emissions, well those emissions are all reabsorbed by the product itself. The complete reabsorption does have a long tail, but if you expose CaO to air it will absorb CO2 all by itself. The rest can be pretty trivially converted to renewable sources so it seems like this is just a big pile of scaremongering nonsense. Which is unfortunate, it is difficult being scientifically literate and progressive being surrounded by people "on your side" who are spouting the exact same kind of nonsense and lies as your opposition.
- cagenut 7y ago
  its to the point where i'm consciously trying to not engage in the facts debate or the what-about-foo endless spiraling. we're over-complicating things and enabling the "debate" to continue to waste precious time. coal need to end within a decade. oil needs to be cut in half within a decade. anything else is a distraction.
  - colechristensen 7y ago
    The problem is already solving itself as well as it can. The world is running out of any fossil fuel except natural gas which can be extracted more cheaply than the various types of renewables. With $100 USD/bbl oil you don't need protests and activism to switch away from fossil fuels, simple economics will drive energy choices. Saudi Arabia is going to run out, and it is likely they have been exaggerating their reserves and production capacity for political reasons. It won't take much to explode the price of oil and people know it and are planning for it.
    - eru 7y ago
      > The world is running out of any fossil fuel except natural gas which can be extracted more cheaply than the various types of renewables. That seems to be sort-of true, but mostly in the sense that renewables are getting cheaper. Fossil fuels don't seem to be getting that much more expensive. Mostly because the long run supply is actually fairly elastic.
      - aoeusnth1 7y ago
        Also, fracking is new huge source of natural gas that wasn't exploitable before.
      - colechristensen 7y ago
        Saudi Arabia claims 250-300 billion barrels of viable oil reserves, and it's currently pumping about 4 billion per year. There is also credible doubt to those numbers with some saying they may be greatly exaggerated for political reasons. It is very possible the all time high of ~11 million barrels a day in Nov 2018 will never be surpassed. There is a lot of oil around to be extracted, it won't "run out" but it is absolutely not elastic, and not at arbitrary prices. The big reserves which remain are considerably more expensive to extract and convert to a usable state. The $100/bbl rate is somewhere around the floor price for the oil economy when those resources dominate. The price of fossil fuels has bounced around in the last decade or two for political reasons. OPEC was forcing prices above $100 because they're a cartel but then North America found an enormous quantity of tar sands and similar kinds of expensive-to-extract but in huge quantities, it was profitable to extract at those prices and OPECs cartel price highs were broken because they could not afford to cut production in order to raise prices (much of OPEC proping up their power with money that they couldn't do without). OPEC is running out of cheap oil, the world is running out of cheap oil. There is an enormous amount of oil left in the ground which can be extracted, but at a price. A price which is easily beatable by renewables now and definitely in the future when scaling and technology factors further lower their prices. Fossil fuels are over, it's done. There's little left to protest or try to change, the situation is forcing it and it can be seen by anybody in the energy business. If you want to burn public money you can accelerate the process a bit with taxes and tech development (this is already being done and it could be done a bit more) but ultimately the future doesn't depend on that, just a bit of timing.
  - mikepurvis 7y ago
    In particular, anything about single-use plastics is mostly a distraction. There's something to be said for the emissions cost of delivering and disposing of them, but in general, sucking oil out of the ground, turning it into plastic objects, and then burying those plastic objects back in the ground is a "complete lifecycle", much more so than releasing that oil's carbon into the atmosphere via combustion. All the more so if the plastic objects are mostly buried alongside other plastic objects where they can be dug up and reprocessed later on as the need arises.
    - XorNot 7y ago
      Except single use plastics don't end up in the ground reliably: they end up in water ways, beaches, wetlands and the oceans. They degrade into micro plastics and then end up in the food chain. They are a huge problem for non-emissions reasons.
      - mikepurvis 7y ago
        Oh yeah, they're definitely a problem, and work should be done to reduce and eliminate them. But they're not directly a climate change problem. Also, if you live in a major western city, especially a non-coastal one, your garbage is pretty reliably ending up in a landfill. 90% of river-borne plastic pollution comes from just 10 rivers, all of which are in Asia and Africa: https://www.weforum.org/agenda/2018/06/90-of-plastic-polluting-our-oceans-comes-from-just-10-rivers/ https://www.weforum.org/agenda/2018/06/90-of-plastic-polluti... This is not a get-of-jail-free card to the rest of the world, but it does change the nature of our responsibility— in particular, it means that individual action is almost entirely worthless. Because the issue in the west is not the trash, it's that we're culturally exporting a single-use lifestyle that creates all that mess when it is imitated in places without the pipeline in place to manage the waste. So what is needed is a collective cultural change in order to alter what we export via our media, and the actions/expectations of our politicians, celebrities, tourists, etc.
  - BenoitEssiambre 7y ago
    Also natural habitats need to be protected. I'm so sick of plastic straw theater though. Plastics barely matter at all for the environment!
- dwiel 7y ago
  Do you have any references on the actual speed of reabsorption? I tried to find some, but didn't have much luck. I've heard numbers as high as 200 years to absorb all of it, but I don't know how "all" was defined for that metric. 90%, 99%, 99.99%? The actual rate of reabsorption is a pretty critical metric here. Even if it only takes 50 or 100 years to absorb half of it, that may not be fast enough as CO2 levels in the next 50 years are still pretty important considering potential feedback loops that could be triggered in that time frame.
- icegreentea2 7y ago
  I think its worth considering how long that long tail is: https://www.cement.org/for-concrete-books-learning/concrete-technology/concrete-design-production/concrete-as-a-carbon-sink https://www.cement.org/for-concrete-books-learning/concrete-... Taking at a look at the link above (which is published by pretty much the more pro-cement group you can imagine), we get that carbon resorption is a thing, that certainly there is a potential for many structures to achieve carbon neutrality over their design lifespans, and that in the "best case", we're talking about 100% carbon neutrality over decades. We also get that 100% carbon resorption is not a design goal of many forms of current reinforced concrete applications since the presence CaC03 increases rebar corrosion. Taken at face value then, what you have is that cement currently emits 8% of all human carbon activity, that over the timespan of decades, it may self sequester itself to 4%, but probably somewhere in between. So even if we trivially converted kiln sources to renewables, there's still probably a decent chunk of carbon emitted in cement creation process that may never be self-sequestered. I think understanding what that final number comes out to would be pretty useful thing to understand, and is hardly scare-mongering. I think once we drill into our heads that we need to decarbonize, after "the easy step" of cutting fossil fuel use, litterally every other form of decarbonization consists of chasing down some carbon source that accounts for the 2-5% range. There will be no low hanging fruit left.
  - BruceM 7y ago
    https://link.springer.com/article/10.1007/s41024-016-0010-9 https://link.springer.com/article/10.1007/s41024-016-0010-9 is a pretty nice discussion of concrete carbonation as well. It is also worth pointing out that the GP's comment was showing the chemistry for a lime-based concrete. OPC (Ordinary Portland Cement) based concrete is substantially different in terms of the chemistry and the amount of energy involved in the manufacturing process (due to the increased amount of energy involved in producing the clinker).
  - colechristensen 7y ago
    I'm not very worried about the remaining carbon producers once fossil fuels become minority energy sources. I think the ability of the biosphere to sink carbon is underestimated as are the benefits of a higher carbon atmosphere. Most talk about anthropogenic climate change are either denying it exists or exaggerating (usually without much knowledge) its negative side effects. Nobody talks about the benefits of expanding the arable land at higher latitudes or increased plant growths in forest (and forests denser and further north). At one point during a carbon spike the planet was more or less covered by jungle pole to pole, how's that for biodiversity? Change is hard and people are always upset about it, but this is a change we have already made for better or worse. There is much doom and gloom about any change and this one will have big consequences but we need to move past arguing about whether or not it will happen and towards how best to respond to it (and in ways other than only desperate attempts to reverse it completely). That doesn't mean there isn't a great benefit to capping the size of the change or to stop the forcing, but at some point you have to accept it and stop treating it as your doom.
- ravenstine 7y ago
  > Which is unfortunate, it is difficult being scientifically literate and progressive being surrounded by people "on your side" who are spouting the exact same kind of nonsense and lies as your opposition. Tell me about it. I once talked to someone who says it's good that people are scaremongering on global warming because otherwise nothing might get done. They say there's no such thing as bad press, but I think it does science a disservice in the long term if perception is that it fails to deliver.
  - deleted 7y ago
    [deleted]
  - TeMPOraL 7y ago
    Press is often not even wrong about climate, and isn't even scaremongering properly. I'd say that accurate scaremongering involves mentioning things like "mass migrations", "loss of habitable land" and "opening up resource-rich areas", which cause things like "humanitarian crisis", "war", "mass starvation" and "collapse of technological civilization". I'd like to see press that dares to mention that.
- coryrc 7y ago
  The reason why is you are wrong. Portland cement, when hardened, does not absorb any significant amount of CO2. It does not form limestone. It mostly forms CSH [0] which just takes water, silicon dioxide, and quicklime. The last is sourced from limestone but does not turn back into limestone. [0] https://en.wikipedia.org/wiki/Calcium_silicate_hydrate https://en.wikipedia.org/wiki/Calcium_silicate_hydrate
  - excessive 7y ago
    Across the world, what percentage is Portland cement vs the other CO2 absorbing kind? I googled around, but couldn't find the answer.
    - aidenn0 7y ago
      Per TFA, 98% of concrete is made from Portland cement.
    - CalRobert 7y ago
      Nearly all, much to the frustration of heritage building owners everywhere. I just spent a few weeks manually chiselling off a godawful cement render from a wall to restore a naturally-hydraulic-lime based one. The cement crap is rock-hard and doesn't have any moisture permeability, so water gets in and just dissolves your building (or more importantly, the old lime-based mortar holding up the dozens of tonnes of stone that is your home)
  - Symmetry 7y ago
    And basically all the other forms of cement in use starting with the Romans. https://rootsofprogress.org/cement-redux https://rootsofprogress.org/cement-redux
- mrfusion 7y ago
  Couldn’t you also easily capture the co2 when making the lime? It seems like it would all be in one place in a controlled environment.
  - Scoundreller 7y ago
    Yes, but you may not have a cavern to compress it into.
  - colechristensen 7y ago
    Easily maybe not, but it would be a great place to start with carbon capture technologies.
  - jsilence 7y ago
    The CO2 is of high quality because it is not coming from a burning something process and there is a huge amount of residual/excess heat from the calcination process. Perfect for algae production!
- zahma 7y ago
  We don't have decades to wait for building stocks to re-absorb the expelled CO2. (Setting aside concrete carbonation, there are better materials to use for building construction. Concrete is a poor insulator, and sourcing other materials will reduce secondary and tertiary energy consumption. Also, buildings can generate energy, but not if they are made of concrete.) I understand that you want to rationalize concrete use via carbonation, but consider the bigger picture. There is simply not a sustainable future in which we continue to build everything with concrete. Perhaps if decision-makers of yesteryear had considered these scientific properties (along with climate change), this could have been included in a comprehensive strategy to limit GHG emissions, but we are well beyond that point and must eliminate CO2 emissions now.
  - eru 7y ago
    We already have lots and lots of building stock carbonating right now. But yes, building has accelerated, so we are not in a steady state. As an interesting aside, tossing lime into the oceans might help. Ignoring the energy costs, once inside the ocean the lime apparently binds twice as much carbon as was released when making it. That process also helps against ocean acidification. So in order for the whole thing to make carbon sense, you'd need to use stranded energy that wouldn't be used for anything else and doesn't release more carbon into the atmosphere, like solar power in a remote desert. And the balance gets even better, if you manage to capture the carbon release by the quicklime making process. See https://en.wikipedia.org/wiki/Enhanced_weathering https://en.wikipedia.org/wiki/Enhanced_weathering and https://en.wikipedia.org/wiki/Iron_fertilization https://en.wikipedia.org/wiki/Iron_fertilization
- deleted 7y ago
  [deleted]
- tito 7y ago
  Here's a relevant article from the publication Nature: "Substantial global carbon uptake by cement carbonation" https://www.nature.com/articles/ngeo2840 https://www.nature.com/articles/ngeo2840 Coverage of Nature letter in the popular press: Concrete products reabsorb nearly half CO2 released in cement manufacture https://www.abc.net.au/news/science/2016-11-22/concrete-is-a-carbon-sink/8043174 https://www.abc.net.au/news/science/2016-11-22/concrete-is-a...
- hannob 7y ago
  > The rest can be pretty trivially converted to renewable sources Your other claim is, as others have pointed out, wrong. But also calling the renewable use in high energy industry "trivial" is quite a stretch. Here's a recent article on the issue that gives you an idea how challenging this is: https://www.vox.com/energy-and-environment/2019/10/10/20904213/climate-change-steel-cement-industrial-heat-hydrogen-ccs https://www.vox.com/energy-and-environment/2019/10/10/209042...
- MauranKilom 7y ago
  The implication "manufacturing cement is a significant contributor to man-made CO2" might be imprecise if most of it were reabsorbed in the final produce. However, I don't see any argument why we should not be trying to absorb this CO2 - sure, concrete could aim to be carbon neutral, but why shouldn't we aim higher?
- Amygaz 7y ago
  You need to add the CO2 released due to energy usage in both processes. It’s quite intensive. I wouldn’t be surprised if over it’s useful life cement only capture an amount equivalent to quarter of what it generates.
cagenut 7y ago
the article mentions cement is 8% of GHG emissions in text, but if you'd like a good visual on that: https://ourworldindata.org/grapher/co2-by-source https://ourworldindata.org/grapher/co2-by-source
- pottertheotter 7y ago
  What an interesting link. Fun to explore how the graph changes between countries or regions. It's interesting that the % from cement is relatively small in the US.
Merrill 7y ago
If cars go electric and there is less demand for gas, oil refineries will produce less asphalt as a byproduct of oil refining. Demand for cement will go up to pave streets for electric cars to run on.
ijiiijji1 7y ago
Actually, the most important part is clinker manufacturing which then leads to Portland cement that leads to concrete. If manufacturing occurred in a sealed chamber and adding a step that consumes or captures carbon emissions would be a logical improvement considering it is a nontrivial amount of GHG emissions. Lime is a close second, but not as important when compared to the energy needs and chemical processes involved in clinker manufacturing.
legulere 7y ago
What's missing from this article is a discussion of rebar. Steel rebar is pretty heavy and rusts easily. With alternative materials you can get longer-lasting structures, that also need to use less concrete.
- rapnie 7y ago
  I really like the idea of using cross laminated timber (CLT) as a full replacement for concrete. It is a radical switch to use wood entirely, even for high-rise buildings, but it is possible, has many benefits, and a good environmental footprint. https://axaxl.com/fast-fast-forward/articles/benefits-and-risks-of-building-with-cross-laminated-timber https://axaxl.com/fast-fast-forward/articles/benefits-and-ri...
einpoklum 7y ago
The article claims implicitly, through the chart, that capture of the CO_2 produced or of the Carbon in it can only reduce emissions by about 10-15%. That is not true. One can definitely bind most of the emitted CO_2. It may make production more costly, and perhaps require larger facilities, but it's definitely possible.
Klapaucius 7y ago
This is a place where carbon capture and storage would be a natural fit. Seriously. Cement is but one example of industrial processes that inherently release large amounts of CO2 even if we were to go 100% renewable energy-wise. Applying carbon-capture technology to cement plants would be a way to actually bring their emissions down to zero regardless. Capturing CO2 directly from such CO2-intensive processes would certainly give way more bang for the buck than trying to capture CO2 out of thin air, as many seems to be placing their hopes on these days. And this is not theoretical. At least here in Norway, it is already being done at one cement plant: https://www.norcem.no/en/CCS https://www.norcem.no/en/CCS
- mikorym 7y ago
  If you combine this with the CO2 capturing aspects of concrete itself as mentioned by other commentators, would that mean you can actually have a net CO2 level decrease?
  - Klapaucius 7y ago
    Theoretically yes, although reasorbtion of CO2 takes a long time.
    - mikorym 7y ago
      We hedge against old buildings then. [1] [1] https://upload.wikimedia.org/wikipedia/commons/d/d3/University_of_Johannesburg.jpg https://upload.wikimedia.org/wikipedia/commons/d/d3/Universi... Quite the concrete jungle...
hinkley 7y ago
There were some studies in using fly ash to reduce the carbon footprint of cement, but it was never clear to me how you avoid point source emissions of fly ash. Isn’t it difficult to handle? They mention fly ash as a resource but don’t cover anything other than that it will also become scarce.

151 points by Reedx 7y ago

This analysis seems to skip the obvious step whereby the manufacture of cement involves expelling CO2 from limestone so that it can be mixed with water which re-forms the same compound by absorbing CO2. Making Lime CaCO3 (+ heat) → CaO + CO2 Making concrete CaO + CO2 (in water, from air) → CaCO3 [there are lots of other things in concrete, but the CaO/CaCO3 are the media that glue them together into the useful composite they are] They quote that as "half" the emissions, well those emissions are all reabsorbed by the product itself. The complete reabsorption does have a long tail, but if you expose CaO to air it will absorb CO2 all by itself. The rest can be pretty trivially converted to renewable sources so it seems like this is just a big pile of scaremongering nonsense. Which is unfortunate, it is difficult being scientifically literate and progressive being surrounded by people "on your side" who are spouting the exact same kind of nonsense and lies as your opposition.

cagenut 7y ago
its to the point where i'm consciously trying to not engage in the facts debate or the what-about-foo endless spiraling. we're over-complicating things and enabling the "debate" to continue to waste precious time. coal need to end within a decade. oil needs to be cut in half within a decade. anything else is a distraction.
- colechristensen 7y ago
  The problem is already solving itself as well as it can. The world is running out of any fossil fuel except natural gas which can be extracted more cheaply than the various types of renewables. With $100 USD/bbl oil you don't need protests and activism to switch away from fossil fuels, simple economics will drive energy choices. Saudi Arabia is going to run out, and it is likely they have been exaggerating their reserves and production capacity for political reasons. It won't take much to explode the price of oil and people know it and are planning for it.
  - eru 7y ago
    > The world is running out of any fossil fuel except natural gas which can be extracted more cheaply than the various types of renewables. That seems to be sort-of true, but mostly in the sense that renewables are getting cheaper. Fossil fuels don't seem to be getting that much more expensive. Mostly because the long run supply is actually fairly elastic.
    - aoeusnth1 7y ago
      Also, fracking is new huge source of natural gas that wasn't exploitable before.
    - colechristensen 7y ago
      Saudi Arabia claims 250-300 billion barrels of viable oil reserves, and it's currently pumping about 4 billion per year. There is also credible doubt to those numbers with some saying they may be greatly exaggerated for political reasons. It is very possible the all time high of ~11 million barrels a day in Nov 2018 will never be surpassed. There is a lot of oil around to be extracted, it won't "run out" but it is absolutely not elastic, and not at arbitrary prices. The big reserves which remain are considerably more expensive to extract and convert to a usable state. The $100/bbl rate is somewhere around the floor price for the oil economy when those resources dominate. The price of fossil fuels has bounced around in the last decade or two for political reasons. OPEC was forcing prices above $100 because they're a cartel but then North America found an enormous quantity of tar sands and similar kinds of expensive-to-extract but in huge quantities, it was profitable to extract at those prices and OPECs cartel price highs were broken because they could not afford to cut production in order to raise prices (much of OPEC proping up their power with money that they couldn't do without). OPEC is running out of cheap oil, the world is running out of cheap oil. There is an enormous amount of oil left in the ground which can be extracted, but at a price. A price which is easily beatable by renewables now and definitely in the future when scaling and technology factors further lower their prices. Fossil fuels are over, it's done. There's little left to protest or try to change, the situation is forcing it and it can be seen by anybody in the energy business. If you want to burn public money you can accelerate the process a bit with taxes and tech development (this is already being done and it could be done a bit more) but ultimately the future doesn't depend on that, just a bit of timing.
- mikepurvis 7y ago
  In particular, anything about single-use plastics is mostly a distraction. There's something to be said for the emissions cost of delivering and disposing of them, but in general, sucking oil out of the ground, turning it into plastic objects, and then burying those plastic objects back in the ground is a "complete lifecycle", much more so than releasing that oil's carbon into the atmosphere via combustion. All the more so if the plastic objects are mostly buried alongside other plastic objects where they can be dug up and reprocessed later on as the need arises.
  - XorNot 7y ago
    Except single use plastics don't end up in the ground reliably: they end up in water ways, beaches, wetlands and the oceans. They degrade into micro plastics and then end up in the food chain. They are a huge problem for non-emissions reasons.
    - mikepurvis 7y ago
      Oh yeah, they're definitely a problem, and work should be done to reduce and eliminate them. But they're not directly a climate change problem. Also, if you live in a major western city, especially a non-coastal one, your garbage is pretty reliably ending up in a landfill. 90% of river-borne plastic pollution comes from just 10 rivers, all of which are in Asia and Africa: https://www.weforum.org/agenda/2018/06/90-of-plastic-polluting-our-oceans-comes-from-just-10-rivers/ https://www.weforum.org/agenda/2018/06/90-of-plastic-polluti... This is not a get-of-jail-free card to the rest of the world, but it does change the nature of our responsibility— in particular, it means that individual action is almost entirely worthless. Because the issue in the west is not the trash, it's that we're culturally exporting a single-use lifestyle that creates all that mess when it is imitated in places without the pipeline in place to manage the waste. So what is needed is a collective cultural change in order to alter what we export via our media, and the actions/expectations of our politicians, celebrities, tourists, etc.
- BenoitEssiambre 7y ago
  Also natural habitats need to be protected. I'm so sick of plastic straw theater though. Plastics barely matter at all for the environment!
dwiel 7y ago
Do you have any references on the actual speed of reabsorption? I tried to find some, but didn't have much luck. I've heard numbers as high as 200 years to absorb all of it, but I don't know how "all" was defined for that metric. 90%, 99%, 99.99%? The actual rate of reabsorption is a pretty critical metric here. Even if it only takes 50 or 100 years to absorb half of it, that may not be fast enough as CO2 levels in the next 50 years are still pretty important considering potential feedback loops that could be triggered in that time frame.
icegreentea2 7y ago
I think its worth considering how long that long tail is: https://www.cement.org/for-concrete-books-learning/concrete-technology/concrete-design-production/concrete-as-a-carbon-sink https://www.cement.org/for-concrete-books-learning/concrete-... Taking at a look at the link above (which is published by pretty much the more pro-cement group you can imagine), we get that carbon resorption is a thing, that certainly there is a potential for many structures to achieve carbon neutrality over their design lifespans, and that in the "best case", we're talking about 100% carbon neutrality over decades. We also get that 100% carbon resorption is not a design goal of many forms of current reinforced concrete applications since the presence CaC03 increases rebar corrosion. Taken at face value then, what you have is that cement currently emits 8% of all human carbon activity, that over the timespan of decades, it may self sequester itself to 4%, but probably somewhere in between. So even if we trivially converted kiln sources to renewables, there's still probably a decent chunk of carbon emitted in cement creation process that may never be self-sequestered. I think understanding what that final number comes out to would be pretty useful thing to understand, and is hardly scare-mongering. I think once we drill into our heads that we need to decarbonize, after "the easy step" of cutting fossil fuel use, litterally every other form of decarbonization consists of chasing down some carbon source that accounts for the 2-5% range. There will be no low hanging fruit left.
- BruceM 7y ago
  https://link.springer.com/article/10.1007/s41024-016-0010-9 https://link.springer.com/article/10.1007/s41024-016-0010-9 is a pretty nice discussion of concrete carbonation as well. It is also worth pointing out that the GP's comment was showing the chemistry for a lime-based concrete. OPC (Ordinary Portland Cement) based concrete is substantially different in terms of the chemistry and the amount of energy involved in the manufacturing process (due to the increased amount of energy involved in producing the clinker).
- colechristensen 7y ago
  I'm not very worried about the remaining carbon producers once fossil fuels become minority energy sources. I think the ability of the biosphere to sink carbon is underestimated as are the benefits of a higher carbon atmosphere. Most talk about anthropogenic climate change are either denying it exists or exaggerating (usually without much knowledge) its negative side effects. Nobody talks about the benefits of expanding the arable land at higher latitudes or increased plant growths in forest (and forests denser and further north). At one point during a carbon spike the planet was more or less covered by jungle pole to pole, how's that for biodiversity? Change is hard and people are always upset about it, but this is a change we have already made for better or worse. There is much doom and gloom about any change and this one will have big consequences but we need to move past arguing about whether or not it will happen and towards how best to respond to it (and in ways other than only desperate attempts to reverse it completely). That doesn't mean there isn't a great benefit to capping the size of the change or to stop the forcing, but at some point you have to accept it and stop treating it as your doom.
ravenstine 7y ago
> Which is unfortunate, it is difficult being scientifically literate and progressive being surrounded by people "on your side" who are spouting the exact same kind of nonsense and lies as your opposition. Tell me about it. I once talked to someone who says it's good that people are scaremongering on global warming because otherwise nothing might get done. They say there's no such thing as bad press, but I think it does science a disservice in the long term if perception is that it fails to deliver.
- deleted 7y ago
  [deleted]
- TeMPOraL 7y ago
  Press is often not even wrong about climate, and isn't even scaremongering properly. I'd say that accurate scaremongering involves mentioning things like "mass migrations", "loss of habitable land" and "opening up resource-rich areas", which cause things like "humanitarian crisis", "war", "mass starvation" and "collapse of technological civilization". I'd like to see press that dares to mention that.
coryrc 7y ago
The reason why is you are wrong. Portland cement, when hardened, does not absorb any significant amount of CO2. It does not form limestone. It mostly forms CSH [0] which just takes water, silicon dioxide, and quicklime. The last is sourced from limestone but does not turn back into limestone. [0] https://en.wikipedia.org/wiki/Calcium_silicate_hydrate https://en.wikipedia.org/wiki/Calcium_silicate_hydrate
- excessive 7y ago
  Across the world, what percentage is Portland cement vs the other CO2 absorbing kind? I googled around, but couldn't find the answer.
  - aidenn0 7y ago
    Per TFA, 98% of concrete is made from Portland cement.
  - CalRobert 7y ago
    Nearly all, much to the frustration of heritage building owners everywhere. I just spent a few weeks manually chiselling off a godawful cement render from a wall to restore a naturally-hydraulic-lime based one. The cement crap is rock-hard and doesn't have any moisture permeability, so water gets in and just dissolves your building (or more importantly, the old lime-based mortar holding up the dozens of tonnes of stone that is your home)
- Symmetry 7y ago
  And basically all the other forms of cement in use starting with the Romans. https://rootsofprogress.org/cement-redux https://rootsofprogress.org/cement-redux
mrfusion 7y ago
Couldn’t you also easily capture the co2 when making the lime? It seems like it would all be in one place in a controlled environment.
- Scoundreller 7y ago
  Yes, but you may not have a cavern to compress it into.
- colechristensen 7y ago
  Easily maybe not, but it would be a great place to start with carbon capture technologies.
- jsilence 7y ago
  The CO2 is of high quality because it is not coming from a burning something process and there is a huge amount of residual/excess heat from the calcination process. Perfect for algae production!
zahma 7y ago
We don't have decades to wait for building stocks to re-absorb the expelled CO2. (Setting aside concrete carbonation, there are better materials to use for building construction. Concrete is a poor insulator, and sourcing other materials will reduce secondary and tertiary energy consumption. Also, buildings can generate energy, but not if they are made of concrete.) I understand that you want to rationalize concrete use via carbonation, but consider the bigger picture. There is simply not a sustainable future in which we continue to build everything with concrete. Perhaps if decision-makers of yesteryear had considered these scientific properties (along with climate change), this could have been included in a comprehensive strategy to limit GHG emissions, but we are well beyond that point and must eliminate CO2 emissions now.
- eru 7y ago
  We already have lots and lots of building stock carbonating right now. But yes, building has accelerated, so we are not in a steady state. As an interesting aside, tossing lime into the oceans might help. Ignoring the energy costs, once inside the ocean the lime apparently binds twice as much carbon as was released when making it. That process also helps against ocean acidification. So in order for the whole thing to make carbon sense, you'd need to use stranded energy that wouldn't be used for anything else and doesn't release more carbon into the atmosphere, like solar power in a remote desert. And the balance gets even better, if you manage to capture the carbon release by the quicklime making process. See https://en.wikipedia.org/wiki/Enhanced_weathering https://en.wikipedia.org/wiki/Enhanced_weathering and https://en.wikipedia.org/wiki/Iron_fertilization https://en.wikipedia.org/wiki/Iron_fertilization
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tito 7y ago
Here's a relevant article from the publication Nature: "Substantial global carbon uptake by cement carbonation" https://www.nature.com/articles/ngeo2840 https://www.nature.com/articles/ngeo2840 Coverage of Nature letter in the popular press: Concrete products reabsorb nearly half CO2 released in cement manufacture https://www.abc.net.au/news/science/2016-11-22/concrete-is-a-carbon-sink/8043174 https://www.abc.net.au/news/science/2016-11-22/concrete-is-a...
hannob 7y ago
> The rest can be pretty trivially converted to renewable sources Your other claim is, as others have pointed out, wrong. But also calling the renewable use in high energy industry "trivial" is quite a stretch. Here's a recent article on the issue that gives you an idea how challenging this is: https://www.vox.com/energy-and-environment/2019/10/10/20904213/climate-change-steel-cement-industrial-heat-hydrogen-ccs https://www.vox.com/energy-and-environment/2019/10/10/209042...
MauranKilom 7y ago
The implication "manufacturing cement is a significant contributor to man-made CO2" might be imprecise if most of it were reabsorbed in the final produce. However, I don't see any argument why we should not be trying to absorb this CO2 - sure, concrete could aim to be carbon neutral, but why shouldn't we aim higher?
Amygaz 7y ago
You need to add the CO2 released due to energy usage in both processes. It’s quite intensive. I wouldn’t be surprised if over it’s useful life cement only capture an amount equivalent to quarter of what it generates.

cagenut 7y ago

the article mentions cement is 8% of GHG emissions in text, but if you'd like a good visual on that: https://ourworldindata.org/grapher/co2-by-source https://ourworldindata.org/grapher/co2-by-source

pottertheotter 7y ago
What an interesting link. Fun to explore how the graph changes between countries or regions. It's interesting that the % from cement is relatively small in the US.

Merrill 7y ago

If cars go electric and there is less demand for gas, oil refineries will produce less asphalt as a byproduct of oil refining. Demand for cement will go up to pave streets for electric cars to run on.

ijiiijji1 7y ago

Actually, the most important part is clinker manufacturing which then leads to Portland cement that leads to concrete. If manufacturing occurred in a sealed chamber and adding a step that consumes or captures carbon emissions would be a logical improvement considering it is a nontrivial amount of GHG emissions. Lime is a close second, but not as important when compared to the energy needs and chemical processes involved in clinker manufacturing.

legulere 7y ago

What's missing from this article is a discussion of rebar. Steel rebar is pretty heavy and rusts easily. With alternative materials you can get longer-lasting structures, that also need to use less concrete.

rapnie 7y ago
I really like the idea of using cross laminated timber (CLT) as a full replacement for concrete. It is a radical switch to use wood entirely, even for high-rise buildings, but it is possible, has many benefits, and a good environmental footprint. https://axaxl.com/fast-fast-forward/articles/benefits-and-risks-of-building-with-cross-laminated-timber https://axaxl.com/fast-fast-forward/articles/benefits-and-ri...

einpoklum 7y ago

The article claims implicitly, through the chart, that capture of the CO_2 produced or of the Carbon in it can only reduce emissions by about 10-15%. That is not true. One can definitely bind most of the emitted CO_2. It may make production more costly, and perhaps require larger facilities, but it's definitely possible.

Klapaucius 7y ago

This is a place where carbon capture and storage would be a natural fit. Seriously. Cement is but one example of industrial processes that inherently release large amounts of CO2 even if we were to go 100% renewable energy-wise. Applying carbon-capture technology to cement plants would be a way to actually bring their emissions down to zero regardless. Capturing CO2 directly from such CO2-intensive processes would certainly give way more bang for the buck than trying to capture CO2 out of thin air, as many seems to be placing their hopes on these days. And this is not theoretical. At least here in Norway, it is already being done at one cement plant: https://www.norcem.no/en/CCS https://www.norcem.no/en/CCS

mikorym 7y ago
If you combine this with the CO2 capturing aspects of concrete itself as mentioned by other commentators, would that mean you can actually have a net CO2 level decrease?
- Klapaucius 7y ago
  Theoretically yes, although reasorbtion of CO2 takes a long time.
  - mikorym 7y ago
    We hedge against old buildings then. [1] [1] https://upload.wikimedia.org/wikipedia/commons/d/d3/University_of_Johannesburg.jpg https://upload.wikimedia.org/wikipedia/commons/d/d3/Universi... Quite the concrete jungle...

hinkley 7y ago

There were some studies in using fly ash to reduce the carbon footprint of cement, but it was never clear to me how you avoid point source emissions of fly ash. Isn’t it difficult to handle? They mention fly ash as a resource but don’t cover anything other than that it will also become scarce.